Conventionally, as a method for manufacturing a honeycombed denitration catalyst using a ceramic fiber sheet, the following Patent Literature 1 by the present applicant discloses a method for manufacturing a denitration catalyst composed of, as a substrate, a honeycomb structure in which a corrugated plate-like ceramic fiber sheet and a flat plate-like ceramic fiber sheet are alternately laminated, which is characterized by dipping the above-described honeycomb structure in a slurry in which titania fine particles are suspended in a silica sol, drying and calcinating the resultant to hold titania and silica simultaneously on the honeycomb structure, further dipping the resulting honeycomb structure in ammonium metavanadate and ammonium metatungstate aqueous solutions in order, thereby supporting vanadium and tungsten on titania.
In addition, as a method for manufacturing a denitration catalyst in which the productivity is more enhanced, and a reduction of cost is achieved, Patent Literature 2 by the present applicant discloses a method for manufacturing a denitration catalyst composed of, as a substrate, a honeycomb structure in which a corrugated plate-like ceramic fiber sheet and a flat plate-like ceramic fiber sheet are alternately laminated, which is characterized by adding ammonium metavanadate and/or ammonium metatungstate to a slurry in which titania fine particles are suspended in a silica sol to adsorb it on titania, subsequently dipping the above-described honeycomb structure in this slurry, and drying and calcinating the resultant to support titania and vanadium and/or tungsten simultaneously on the honeycomb structure.
Furthermore, Patent Literature 3 by the present applicant discloses a slurry for manufacturing a denitration catalyst containing a silica sol, titania particles, and ammonium metavanadate and/or ammonium metatungstate, which is characterized in that its pH is adjusted with an ammonia aqueous solution to from 3.5 to 6.0.
As a method for enhancing abrasion resistant strength of an edge of the honeycombed denitration catalyst described in such Patent Literature 2 or 3, the following Patent Literature 4 by the present applicant discloses a method for hardening treatment of a catalyst edge, which is characterized in that in forming a coating layer of a ceramic having a higher hardness than the catalyst on a surface of an edge of the side in which the gas flow of the honeycombed catalyst, the edge of the catalyst is dipped in an immersion slurry for forming a coating and dried to form a coating layer, and subsequently, the coating portion is dipped in a metal salt aqueous solution, dried and then calcinated.
In addition, in the case where the supporting amount of the catalyst component is low, and hardening of the end surface is insufficient in the method of the above-described Patent Literature 4, the following Patent Literature 5 by the present applicant discloses, as a method for effectively enhancing the abrasion resistant strength of the end surface, a method for manufacturing a catalyst, which is characterized by conducting (i) a step of dipping an end surface portion of a support structure having a catalyst component supported thereon in a metal salt aqueous solution in a concentration from 2.7 to 3.88 moles/L in terms of mole of the metal; (ii) a step of drying; (iii) a step of again dipping in a metal salt aqueous solution of the same metal species as that described above in a concentration from 2.7 to 3.88 moles/L in terms of mole of the metal; and (iv) a step of conducting a calcination treatment to harden the catalyst end surface in order. In the method described in this Patent Literature 5, a solid content is dispersed in an ionic or molecular state in the metal salt aqueous solution and intrudes into and is deposited on fine cracks on a surface of the catalyst layer which will become a cause of abrasion by dust particles, thereby increasing the abrasion resistant strength due to a binder effect.